pow, powf, powl - power function

Syntax	#include <math.h> double pow(double x, double y); C11 float powl(float x, float y); long double powl(long double x, long double y); (End)
	These functions compute the value xy.  x is the base of the exponential function (a floating-point number). y is the exponent (also a floating-point number). If x is 0, y must be positive; if x is negative, y must be an integer value.
Return val.	Value of xy	if x, y and the result lie in the permitted floating-point interval.
	+/-HUGE_VAL +/-HUGE_VALF +/-HUGE_VALL	depending on the function type and the sign of x, if an overflow occurs. errno is set to indicate the error.
	1.0	if x and y are both 0.
	-HUGE_VAL -HUGE_VALF -HUGE_VALL	depending on the function type, if x is 0 and y is less than 0. errno is set to indicate the error.
	undefined	if x is less than 0 and y is not an integer. errno is set to indicate the error.
Errors	pow(), powf() and powl() will fail if:
	EDOM	The value of x is negative, and y is not an integer. The value of x is 0, and y is negative.
	ERANGE	The value of x would cause an overflow.
See also	exp(), hypot(), log(), log10(), sinh(), sqrt(), math.h.